Desorption of gases

Extensive work has been done on corrosion inhibitors (140), activated carbon use (141—144), multiple absorption zones and packed columns (145,146), and selective absorption and desorption of gas components (147,148). Alkan olamines can also be used for acid gas removal in ammonia plants (149). 

Plot of pressure, if no measurable gas is desorbed from the walls 2, plot of pressure, if desorption of gas stops after 2 h at a pressure of 0.08 mbar 3, plot of pressure if desorption of gas stops after 3 h at a pressure of 0.14 mbar. 

The leak rates of a freeze drying plant can be measured at the empty plant with the condenser cooled and the shelves heated by measuring the pressure rise per time multiplied by the installation volume in the dimension (mbar L/s). It should be noted, that the plant has to be evacuated for several hours, e. g. down to 10-2 mbar, before the pressure rise measurements, to avoid the influence of small amounts of ice and the desorption of gas from the surfaces. Furthermore, the pressure rise should be measured up to 0.2 or 0.4 mbar to detect possible gas desorption. Only if the pressure rise has been for some time proportional with time (Fig. 2.33.1), it represents a leak rate, which is defined as... 

In many practical applications, gas-liquid mass transfer plays a significant role in the overall chemical reaction rate. It is, therefore, necessary to know the values of effective interfacial area (aL) and the volumetric or intrinsic gas-liquid mass transfer coefficients such as kLah, kL, ktaL, kg, etc. As shown in Section IX, the effective interfacial area is measured by either physical e.g., photography, light reflection, or light scattering) or chemical methods. The liquid-side or gas-side mass-transfer coefficients are also measured by either physical (e.g., absorption or desorption of gas under unsteady-state conditions) or chemical methods. A summary of some of the experimental details and the correlations for aL and kLaL reported in the literature are given by Joshi et al. (1982). In most practical situations, kgaL does not play an important role. 

Based on the same assumptions as for the ideal-lattice-gas equation, Langmuir in 1918 derived Eq. (14.106) by noting that at equilibrium the rate of adsorption arrd the rate of desorption of gas molecules must be the same. For monolayer adsorption, the number of sites may be divided into the fraction occupied0 and the fraction vacant 1 — 0. By definition. 

The role of thermal energy would be considered such as, a) the thermal energy activates the Ga-CH3 bond scission in the hot trimethylgallium molecules, and/or b) the thermal energy facilitates the desorption of Ga atoms generated photochemically from the substrate, etc. 

In the conventional approach, the rate of mass transport between adsorbed gas in the matrix and free gas in the cleats and other fractures is assumed to involve a two-step process corresponding to desorption/diffusion within the coal matrix, followed by long-range flow in the cleat system. Desorption of gas from the coal surface occurs at a much faster rate than the diffusion of the gas through the coal matrix. The rate of diffusion is often assumed to be sufficiently represented by Fickian diffusion which is usually the rate-limiting step in the desorption process. 

An interesting example is given by the adsorption and the desorption of gas. The filling of a tank or a truck tank with gas leads to an emission of pollutants into the air. The treatment is achieved with filters of activated carbon grains or cloths and the desorption is performed at low pressure between 200 and 500 mm Hg. The solvent stream is then absorbed in liquid gas. 

The initial reactant product conversion rate should increase at higher temperature because kinetic rate constants for elementary steps, particularly the desorption of gas D, increase at higher temperature. In summary, there is no total pressure dependence of the initial reactant product conversion rate when (1) A -h B C -h D, (2) single-site adsorption is appropriate for each component, and (3) desorption of one of the products controls the Hougen-Watson kinetic rate law. 

This article mainly introduce based on micro electro mechanical system (MEMS) flow sensor FS4001-200—CV—CH4 desorption of gas in coal bed recorder in the research and design method. For trace, low pressure loss and the volume of a gas flow velocity measurement. 

ABSTRACT In order to investigate the effect of coal particle size on gas desorption and diffusion law at constant temperature, the constant temperature dynamic coal particle gas adsorption and desorption experiment with different particle sizes was conducted in the coal gas adsorption and desorption experiment system. The results suggest that gas desorption laws of different particle size of coal samples show a good consistency at different pressures, and the cumulative desorption of gas coal particle is linear with time. For the same particle, the higher the initial pressure, the more the maximum gas desorption the smaller the coal particle is, the more quickly the gas desorption rate is at the same initial pressure. Then, the gas spherical flow mathematical model is built based on Darcy law and is analysed with finite difference method. At last, the gas spherical flow mathematical model is constructed with Visual Basic. The contrast between numerical simulation and experimental results shows that the gas flow in the coal particle internal micropore accords with Darcy s law. 

The coal particle radius is 0.27 mm and its permeability coefficient is 1 x 10 mV(MP s). Gas adsorption parameters are obtained by analyzing the experimental results, a is 27.32 mVt, b is 0.35 MPa" and the coal density is 1.2 mVt. The gas flow equation is calculated with the program designed by VB based on the experimental parameters and the dimensionless cumulative desorption of gas is obtained. Then the dimensionless time and the dimensionless cumulative desorption are translated into dimension time and dimension cumulative desorption. 

Case 4. The desorption of gas from a membrane is an equally important example of the apjjlication of equation (51). Suppose at the time t = 0 the membrane contains a uniform concentration Cq of solute throughout, from a = 0 to a = Z and C l = 2 = solution in this case by substitution in (51)... 

I must emphasize that before a detector is warmed, the HV must be switched off. If, as should be the case, the preamplifier HV cutout is connected, that will automatically switch off the HV as the temperature rises. However, when the detector cools down again, it would be preferable that the HV did not switch on again automatically without the user being satisfied that thermal equilibrium is established. (There is a hazard that if a pressure rise occurs, due to desorption of gas, and this happens with HV applied, there could be damaging electrical discharges.) A recommended procedure is as follows ... 

Further, it is thus apparent that in gas recovery from shale, the desorption of gas (mainly methane, CH4) will be determined by the surface forces. 

To confirm the four-stage scenario mentioned earlier, we have developed a quantitative model. The model is required to account for adsorption and desorption of Ga, for the formation of excess Ga interacting with the Ga adlayer and for GaN growth in the case of the simultaneous presence of Ga and N. Our model, in units normalized to the maximum Ga-adlayer coverage, is described by the following equations ... 

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